Power supply system for carrier communication systems



April 27, 1948. R. KELLY 2,440,275

POWER SUPPLY SYSTEM FOR CARRIER COMMUNICATION SYSTEMS Filed July 12,1943 Inventor Rickard Az/ly Patented Apr. 27, 1948 v POWER SUPPLY SYSTEMFOR CARRIER COMIWUNICATION SYSTEMS Richard Kelly, London, England,asslgnor to Standard Telephones and Cables Limited, London, England, aBritish company Application July 12, 1943, Serial No. 494,343 In GreatBritain August 7, 1942 2 Claims. (01. 175-363) This invention relates topower supply systems for multi-channel carrier systems and has for itsobject to provide such a system in which the regulation of the voltagerequired for the thermionic valves of the system is carried out in animproved manner.

A well known arrangement for the regulation of the voltage of a supplycomprises a space discharge regulator device in the form of a threeelectrode thermionic valve in series with the load circuit, theimpedance of the device being controlled to compensate for changes involtage across the load circuit. For this purpose the grid of this valveis controlled by a potential varying according to that across the load.It has been proposed, in order to avoid the variation of grid biasbatteries with time to raise the .cathode of this valve to a standardpotential with respect to one of the load circuit terminals by means ofa potential derived from the potential across a gas-filled tubeconnected in shunt to the supply. I have found, however, that thepotential across a gas-filled tube is unstable and cannot be relied uponfor such purpose.

According to the present invention I provide a power supply system for amulti-channel carrier system in which the high tension direct voltage orvoltages is or are derived from an alternating current supply throughrectifiers and are regulated by applying a potential varying accordingto the load circuit voltage and a bias potential to the grid of athermionic valve in opposition, the anode voltage of which valvecontrols the impedance of a space discharge regulator device in serieswith the load circuit and in which the said bias potential is obtainedfrom the said alternating current supply after passing through a staticregulator of the saturating choke type and through a separatetransformer secondary and separate rectifier from that or thosesupplying the said high tension direct voltage or voltages.

One embodiment of the invention will be described as applied in a powersupply system for a multi-channel carrier telegraph system in which therequirements as to voltage regulation are especially severe.

In a multi-channel carrier telegraph system high tension direct voltagesare required not only for application to the anodes of the thermionicvalves forming the carrier transmitters and receivers but also for thevoltages by which the relays of the direct current telegraph channelsmodulate the carrier currents and for the voltages to be applied to thedirect current telegraph channels in accordance with received carriersignals. These direct voltages are plus and minus voltages equallyremoved from zero and it is pre ferred to obtain the plus and minusvalues separately, i. e. through separate transformer secondaries andrectifier bridges, and to regulate each by means of an individual spacedischarge regulator device the impedance of which is controlled by anindividual thermionic valve. The bias potential for the grid of thethermionic valve for the regulation of one of these voltages, e. g. theminus voltage, is obtained directly from the alternating current in themanner above mentioned, but preferably the bias potential for theregulation of the other of these voltages, the plus voltage, is obtainedfrom the regulated output of the minus voltage, in order that, if thereis any slight variation the plus and minus voltages shall vary together.

The system shown in the accompanying drawing is the first power supplysystem for a multichannel carrier telegraph system of which I am awarein which satisfactory operation has been obtained without the use ofbatteries. This system has been found to be better than prior systemsusing batteries.

Referring to the drawing, the alternating current mains are connected tothe terminals A, A and when the switch Si is closed alternating currentis supplied to a plurality of transformer primaries in parallel. Thepower supply for the cathode heaters of the valves of the carriertelegraph transmitters and receivers is obtained at terminal pair E1,E1" from a transformer Ti and rectifier bridge W9, the supply beingsmoothed by inductance Li and condenser Cl. The anode voltages for thevalves in the carrier telegraph transmitters and receivers is suppliedto terminal pair E3, E3" through transformer T3 and rectifier bridge W3,being regulated in a manner described hereafter. Voltages of volts and-80 volts required for the D. C. telegraph transmitters that modulatethe carrier transmitters and for the voltages to be applied to the D. C.channels by the carrier receiving circuits are obtained at terminalpairs E5, E5", and E7, E1 through transformers T5, Tl and rectifierbridges W4 and W5 respectively and regulated in a manner describedhereafter. A bias voltage of volts required for the regulators for theanode voltages and the D. C. telegraph transmitter voltages is obtainedat terminal pair E2, E2" through transformer T2 and rectifier bridge W2,resistances RI, R2 and condenser C2 being connected beyond the rectifierbridge W2 to erminals Ea and E9 for a purpose to be explained. Afterhaving brought one terminal of each of the above-mentioned thermionicpairs to a common potential, the outgoing terminals are indicated at EI,E3, E5, and El. 7

. The terminals of the primary of transformer Ti and terminals oftransformer T2 are connected to the supply terminals A A through a regulating transformer T1 of known kind, operating on the saturated chokeprinciple, which provides an output which is stable within narrow limitsdespite variations in the mains supply, and through switch SI. Terminalsa, a" of the primary of transformer T3 and terminals e, e" of theprimaries of transformers TI and T1 are connected through switch SI tothe supply terminals A, A without the interposition of a resulator butinterposed in one lead are normally open contacts b3 of a relay whichforms part of a time delay arrangement hereinafter described.

The supply of --80 volts for the D. C. telegraph transmitters isobtained through transformer Tl and rectifier bridge W5 followed by asmoothing filter Ll, CI 0, C5. Condenser C I and inductances L4 arearranged to beresonant at 100 cycles and thus decrease the voltageacross C5 at low loads. The output from this filter is regulated in thefollowing manner. In one of the leads is connected a resistance R23 anda thermionic valve regulator VII in series. Although only one valve isshown it is to be understood that a plurality of valves in parallel thenumber depending upon the load may be used e. g., for a current of 0.55ampere, six valves are connected in parallel, and there are sixresistances R23. The grid of valve VII is connected through resistanceR" to the anode of valve VI 9 (there are as many resistances RI I asthere are valves VII) the cathode of which is connected to the otherlead from bridge W5. Valve ,VI9 is shown as a pentode with thesuppressor grid connected to the control grid, and the screen gridbiassed by a potentiometer Rl8, RIS across the smoothed output ofrectifier bridge W5. The control grid is connected through resistancesR20, R21 to a point on a potentiometer P3 which is connected between thepositive side of the load and the negative side of the rectified andsmoothed supply from transformer T2 and recti fier bridge W2.

Any decrease in load current or increase in mains voltage causes anincrease in voltage across the smoothing condenser C! which tends tocause '4 voltage higher current supply that would be needed if a fixedpotential were applied to the cathode of VIE.

Fluctuations between full load and no-load which occur inlthe D. C.telegraph circuits are reduced inefi'ect by the provision'of aresistance R22 of 8,000 ohms as a dummy'load.

Fbr simplicity and economy the heater voltages of the valves VII and VI9are not regulated. The cathode of the valve VII is a directly heatedfilament supplied from terminals 9, g. of the secondary of transformerT6. The cathode of valve VI 9 is indirectly heated, the heater beingconnected to terminals k, k; on the secondary of the transformer T6. Theelectron emission from the oathodes of these valves changes withvariation in the mains supply and to compensate for this a slightincrease in the negative bias voltage with increase in the voltage ofthe mains supply is desirable and is most easily accomplished when, asin the arrangement shown, the reference voltage is applled as a bias tothe grid. Since valve VII becomes conducting im mediately potential isapplied to its anode and current to its filament, whilst VI9 requires aninterval, whilst the cathode is heating up to become conducting,precautions are taken to prevent the supply being connected to theprimary of transformer T7 until the cathode ofthe load voltage toincrease. ,The grid of valve V I9 will tend to become more positive andthe anode potential of valve VIS will decrease. The

to the cathode, as is the more usual arrangement.

no resistance is requiredv in the cathode circuit. which resistance whenpresent has an autobias effect, thus adversely effects the operation ofthe control valves. I 1

Moreovenby applying the reference voltage as a bias on the grid of VIQthe supply from transformer T2 becomes a high voltage low current supplywhich is more easily'smoothed by the re-.

valve Vi9 has had time to heat up. Otherwise are initially open. Asynchronous motor M is set in operation over normally closed contacts172 of the relay Attached to the rotor of the motor is a revolv- I ingarm which makes momentary contact with two studs in succession. In theposition shown nothing happens but when the arm comes on to the nextstud, relay v operates, and closes contact a2 and a locking circuit foritself over contacts aI front and hi 7 back. When the arm again reachesthe position 7 shown, relay operates," closed a -locking circuit foritself over contactsb'i, breaks the circuit of relay at the samecontacts. and forthe motor M at.

contacts b2, andat front contactsb3 connects the A. C. to the terminalse'e" of transformer *TI. The rectifier W8 allows relay to remainoperateduntil relay B has time to close sistance capacity filter RIRLCZthan the low its locking circuit.

The-current for the operation of relays A B i and is obtained from thesmoothed output of trans-v former TI and rectifier bridge WI. mainsfailure occurs, relay Thus if a delay is arranged to be 50 seconds.

In a telegraph supply it is necessary to maintain the difference betweenthe positive and negative sides of the D. C. circuits within very closelimits; and although the actual voltage should be kept approximately tothe nominal the allowable deviation is greater the more closely the andsides of the D. C. circuits are balanced. ,In the arrangement shown thebias on the grid of the valve V18 which regulates the supply forthepositive side of the D. G. circuits is biassed from a potentiometerRid. P2, R21 connected across the outputs of the positive and negativeD. C. supplies in series. Any change in the load to the negative circuitwill be reflected to the regulator of the positive load and a balance ofvoltages results.

The voltage of +80 required for the D. C. telegraph transmitters isderived from the transformer T5 and rectifier bridge W4, is smoothed byinductances L3 and condenser C9 and C4 (arranged in the same manner asinductances Ld and condensers Gill and C5) and is regulated in themanner above described by valve Vl0- controlled by a valve V18. The biasvoltage for the grid of valve W8 is derived from potentiometer P2 whichis in series with resistances RM and R2! between the positive terminalof the +80 v. and the negative terminal of the 80 v. load circuits.manner as R22.

The voltage required for the anodes of the valves in the carriertelegraph system is obtained from a transformer T3 and rectifier bridgeW3, smoothed by an inductance L2 and condenser C3 and regulated by avalve V4, which is controlled by a valve Vll. The grid bias of valve Vllis obtained in the same manner as that for valve Vl9, the grid beingconnected to a point on a potentiometer PI between the positive side ofthe load and the 100 v. obtained from transformer T2 and rectifierbridge W2.

It should be observed that valves V4 and V10 are in practice, each aplurality of valves connected in parallel.

As pointed out above the bias potential for the valves V11, V18 and V19is subjected only to the regulation of .the static transformer T8 andsmoothing circuit RI, R2, C2, whilst the supply for cathode heaters ofthese valves is not subject to such regulation. An increase in mainsvoltage causes increases inthe voltage across the heaters of thecathodes of valves V I1, W8 and A dummy load R15 is used in the same W9,this causes an increase in the potential drop across resistances R3, BIGand RI! and thus an increase in the bias applied to valves V4, V10 andvii. A decrease in output voltage results. The bias potential applied tothe grids of valves Vl'l, V18 and V19 also increases with increase inmains voltage. This increase in bias potential serves to compensate forthe increased emission from the cathodes.

The supplies for the various voltages required have been shown asderived through separate transformers but this is merely a matter ofconvenience and transformers Ti and T2 on the one hand and T2, T5, T6and TI on the other hand may have a common primary and separatesecondary windings.

What is claimed is:

1. In a power supply system for a multichannel carrier system in whicheach high tension direct current voltage controlling a load circuit isderived from an alternating current supply through a transformer andrectifier, regulation being obtained by controlling the potentials of athermionic valve having a plurality of grids, the anode voltage of whichcontrols the imped ance of a space discharge regulator device connectedin series with the load circuit, the com bination therewith comprisingmeans for deriving a bias reference potential, said means furthercomprising a separate transformer having a primary connected to saidalternating current supply and a secondary, a static regulator of thesaturable choke type connected in said primary, a rectifier connected insaid secondary, means for deriving a potential in opposition to saidreference potential, said opposition potential varying according to thepotential across the load circuit, and means for applying said referencepotential and said opposition potential to the input of said thermionicvalve.

2. A power supply system in accordance with claim 1, further comprisingmeans for supplying cathode potentials to said thermionic valve andmeans responsive to said separate transformer energization for delayingthe energization of said space discharge regulator device with respectto said cathode supply potentials.

RICHARD KELLY.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Johnson June 5, 1945

